3.3.1. Standardization of conditions for efficient dehairing
Complete dehairing processes were standardized and opti-
mized using concentrated B. licheniformis protease which resulted
in 2% (w/v) for goat skin, 1% (w/v) for sheep skin and 5% (w/v) for
the buffalo hide gave complete dehairing within 12 h (Table 3,
Fig. 4C, D). Efficient dehairing was obtained at pH value of 8 and 9
in 8 h. However, at pH value of 10 the period of dehairing
increased to 12 h or even more. At pH value of 7.0, hundred
percent dehairing was not observed even after 24 h of incubation.
The
original pH of the concentrated protease is around 8.0, and
since complete dehairing was observed at pH value of 8.0, thus
there was no need of addition of any NaOH for pH adjustment.
At 30
C and above temperatures, 100% dehairing was observed in
8e10 h in sheep and goat skin and 10e12 h for buffalo hide. Even
though 100% dehaing was observed at 25
C, the incubation time
was much longer up to 24 h. Thus, this protease could also be
efficiently used for dehairing in tanneries in cold countries where
the ambient temperature is around 25
C. This also is an effort to
make the beam house operation of the tannery completely green
without the assistance of any chemicals.